Integrated circuits are commonly fabricated using semiconductor substrates. Numerous processes are used in the fabrication of the circuits, including, for example, deposition of material, etching of material, doping, photolithography, metallization, oxidation, etc. Most often, a plurality of identical integrated circuits are formed over a single substrate, commonly referred to as a wafer, to define individual circuit die. These are ultimately singulated into separated die or chips, which are then packaged. In other applications, a single wafer or other substrate might be fabricated to comprise one or more different integrated circuits, and may not be singulated. Regardless, a continuing goal in the fabrication of integrated circuitry is to make ever denser and smaller devices, and resultant integrated circuitry.
One manner of increasing density in a semiconductor assembly is to stack individual substrates, such as semiconductor die, one upon another. The stacked semiconductor die may be interconnected by forming conductive vias in through holes in one or more of the semiconductor dies, for example prior to singulation. An interior of each of the vias may be coated with an electrically insulating material followed by an electrically conductive material to electrically connect the vias to integrated circuitry fabricated on a primary circuitry side of the substrate. Thus, the conductive vias provide a conductive pathway from the primary circuitry side of a semiconductor substrate to its back-side or back-surface for conductive contact with another substrate.
The integrated circuit die, when near completion and prior to singulation, are usually provided with one or more dielectric passivation layers on one or both sides of the substrate. Such layers might provide one or more of insulative protection, stress buffering, and/or a moisture barrier to underlying circuitry. The through hole vias are then formed through the passivation layer(s) and into semiconductive and other material of the substrate. As above, in order to isolate the conductive portion of the through substrate interconnect from other portions of the substrate, the vias are lined with one or more electrically insulating materials. As the throughway for vias become narrower, it can be problematic to completely line sidewalls of such vias with dielectric material prior to forming conductive material therein. One existing manner of doing so comprises pulsed chemical vapor deposition of an aluminum oxide-comprising material. Such is deposited over the dielectric layer and into the via to line the sidewalls of the via. Differences in thermal coefficients of expansion among the aluminum oxide-comprising material, the passivation dielectric material and materials of the substrate can undesirably cause separation and cracking or one or more of these materials.